Mutations in MDH2, Encoding a Krebs Cycle Enzyme, Cause Early-Onset Severe Encephalopathy

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• 作者：Samira Ait-El-Mkadem¹ ; ² ; ¹⁸ ; Manal Dayem-Quere¹ ; ² ; ¹⁸ ; Mirjana Gusic³ ; ⁴ ; ¹⁸ ; Annabelle Chaussenot¹ ; ² ; Sylvie Bannwarth¹ ; ² ; B&eacute ; reng&egrave ; re Franç ; ois² ; Emmanuelle C. Genin² ; Konstantina Fragaki¹ ; ² ; Catharina L.M. Volker-Touw⁵ ; Christelle Vasnier⁶ ; Val&eacute ; rie Serre⁷ ; Koen L.I. van Gassen⁵ ; Franç ; oise Lespinasse² ; Susan Richter⁸ ; Graeme Eisenhofer⁸ ; C&eacute ; cile Rouzier¹ ; ² ; Fanny Mochel⁹ ; Anne De Saint-Martin¹⁰ ; Marie-Th&eacute ; r&egrave ; se Abi Warde¹⁰ ; Monique G.M. de Sain-van der Velde¹¹ ; Judith J.M. Jans¹¹ ; Jeanne Amiel¹² ; Ziga Avsec¹³ ; Christian Mertes¹³ ; Tobias B. Haack³ ; ⁴ ; Tim Strom³ ; ⁴ ; Thomas Meitinger³ ; ⁴ ; Penelope E. Bonnen¹⁴ ; Robert W. Taylor¹⁵ ; Julien Gagneur¹³ ; Peter M. van Hasselt¹⁶ ; Agn&egrave ; s Rö ; tig¹⁷ ; Agn&egrave ; s Delahodde⁶ ; Holger Prokisch³ ; ⁴ ; Sabine A. Fuchs¹¹ ; V&eacute ; ronique Paquis-Flucklinger¹ ; ² ; ^{paquis@hermes.unice.fr}
• 刊名：The American Journal of Human Genetics
• 出版年：2017
• 出版时间：5 January 2017
• 年：2017
• 卷：100
• 期：1
• 页码：151-159
• 全文大小：1185 K
• 卷排序：100

文摘

MDH2 encodes mitochondrial malate dehydrogenase (MDH), which is essential for the conversion of malate to oxaloacetate as part of the proper functioning of the Krebs cycle. We report bi-allelic pathogenic mutations in MDH2 in three unrelated subjects presenting with early-onset generalized hypotonia, psychomotor delay, refractory epilepsy, and elevated lactate in the blood and cerebrospinal fluid. Functional studies in fibroblasts from affected subjects showed both an apparently complete loss of MDH2 levels and MDH2 enzymatic activity close to null. Metabolomics analyses demonstrated a significant concomitant accumulation of the MDH substrate, malate, and fumarate, its immediate precursor in the Krebs cycle, in affected subjects’ fibroblasts. Lentiviral complementation with wild-type MDH2 cDNA restored MDH2 levels and mitochondrial MDH activity. Additionally, introduction of the three missense mutations from the affected subjects into Saccharomyces cerevisiae provided functional evidence to support their pathogenicity. Disruption of the Krebs cycle is a hallmark of cancer, and MDH2 has been recently identified as a novel pheochromocytoma and paraganglioma susceptibility gene. We show that loss-of-function mutations in MDH2 are also associated with severe neurological clinical presentations in children.